At present, solid-state illumination devices using light emitting diodes (LED), semiconductor laser elements, and the like are studied actively as illumination devices serving as an alternative to fluorescent lamps. Since these solid-state illumination devices are mercury-free light emitting devices not using mercury harmful to the human body, they are attracting attention as environment-friendly devices.
FIG. 11 is a cross sectional view showing one form of a conventional light emitting device using a semiconductor laser element.
As shown in FIG. 11, the conventional light emitting device is fabricated by mounting a submount 32 packaging a semiconductor laser element 31 on a stem 33, providing a cap 34 onto them, welding cap 34 to stem 33, and sealing semiconductor laser element 31. Cap 34 has a base section having a hole for taking out light and a glass section 35 covering the hole, and glass section 35 is mounted inside the base section.
FIG. 12 is a cross sectional view showing another form of a conventional light emitting device using a semiconductor laser element. The light emitting device shown in FIG. 12 is a light emitting device obtained by further adding the function of a wavelength conversion element and the like to the light emitting device of FIG. 11. That is, the light emitting device shown in FIG. 12 has a structure in which a functional film having a function such as the function of a wavelength conversion element is provided on a surface of a glass section. The light emitting device is fabricated by soldering a submount 62 packaging a semiconductor laser element 61 onto a base 63, welding a cap 64 onto base 63, and thereby sealing semiconductor laser element 61.
Cap 64 has a base section having a hole for taking out light and a glass section 65 covering the hole, and glass section 65 is mounted inside the base section of cap 64. Further, a wavelength conversion element 66 and a functional film 67 are provided on a surface of glass section 65, and functional film 67 has a photocatalytic effect by receiving light with a specific wavelength.
With a structure as described above, a portion of light 68 emitted from semiconductor laser element 61 is wavelength-converted by wavelength conversion element 66, and a photocatalytic effect is obtained on a surface of functional film 67 by the wavelength-converted light. The photocatalytic effect can suppress foreign matter from attaching to a surface of a package of the light emitting device and deteriorating properties of the light emitting device.